Snap acting bimetal heatmotor valve operator

ABSTRACT

A heatmotor operator comprising a bimetal assembly having a bimetal motor arm connected with a bimetal compensating arm through an insulator, a lever carrying a magnet which is disposed between primary and secondary armatures, the lever being connected to the bimetal assembly and a pivot pin, and actuating means connected with the bimetal assembly whereby the bimetal assembly is actuated to move the lever and cause the magnet to move with snap action from the primary armature to the secondary armature.

United States Patent Inventors Hollis L. Randolph Lakewood; Bradford N. Hull, Long Beach; William W. Chambers, Anaheim, Calif.

Appl. No. 813,684

Filed Apr. 4, 1969 Patented Jan. 19, 1971 Assignee Robertshaw Controls Company Richmond, Va. a corporation of Delaware SNAP ACTING BlMETAL HEATMOTOR VALVE OPERATOR 10 Claims, 16 Drawing Figs.

U.S.Cl 251/11, 3 10/4; 60/23 Int. Cl F03g 7/06, .6 23 9 Field of Search w 316/1;

[56] References Cited UNITED STATES PATENTS 2,743,574 5/1956 McCorkle 25 l/ll 3,275,285 9/1966 Morris 251/11 Primary Examiner-Arnold Rosenthal AttorneysAuzville Jackson, Jr., Robert L. Marben and Christen, Sabol & OBrien ABSTRACT: A heatmotor operator comprising a bimetal assembly having a bimetal motor arm connected with a bimetal compensating arm through an insulator, a lever carrying a magnet which is disposed between primary and secondary armatures, the lever being connected to the bimetal assembly and a pivot pin, and actuating means connected with the bimetal assembly whereby the bimetal assembly is actuated to move the lever and cause the magnet to move with snap action from the primary armature to the secondary armature.

FIG. I

58 IO 32 28 3o 48 66 68 8O 88 24 42 as 4446 60 7e l6 FIG. 2

INVENTORS HOLLIS L. RANDOLPH BRADFORD N. HULL 7 WILLIAM W. CHAMBERS ATTORNEYS PATENTEIIJIIIIQIIIII I v 2 sutnzIIFa 42 28 50 I Q 30 i v 52 I I I0 FIGS VENT I HOLLIS ANDO BRADFORD N. HULL WILLIAM w. CHAMBERS MWUW ATTORNEYS PATENTEU .mn slsm 3 4 sum 3 or 4 I2 Q)" IE; 24 42 I40 FIG. 7

INVENTORS HOLLIS L. RANDOLPH BRADFORD N. HULL FIG. IO WILLIAMW. CHAMBERS M We v ATTORNEYS PATENTEUJANI 9 l9?! 3; 556; 462

- sum u BF 4 INVENTORS HOLLIS L. RANDOLPH BRADFORD N. HULL M )ffl v/ff' $6M ATTORNEYS WILLIAM w. CHAMBERS SNAP ACTING BIMETAL HEATMOTOR VALVE OPERATOR BACKGROUND OF THE INVENTION It is desirable to construct heatmotor operators so that they are snap acting to avoid gradual or steplike'operation which is not acceptable in electric switch andvalve controls for obvious reasons. While many conventional heatmotor operators are designed to be snap acting, the conditions under which they will properly operate are so limited as'to render them infeasible and in some cases dangerous when utilized with equipment or in systems where accurate control is required.

The ineffectivenessof conventional heatmotor operators in controlling valves is particularly acute because failure of the valve to operate or gradual opening or closing of the valve can precipitate potentially dangerous situations, especially with respect to valves used to control theflow of gas in heating and air-conditioning systems. Moreover,,ina ccurate operation of valves is uneconomical and can cause the failure of entire systems.

On prior art heatmotor operatorutiliz'ed as a valve control comprises a bimetal assembly which is directly coupled with a valve member or valve stem such that at high and low ambient temperatures a valve member has a tendency to tip and a valve stem has a tendency to be cocked in its bushing which cause gradual opening and closing of the valve. Other prior art heatmotor operators utilize a compensating bimetal along with a motor bimetal to compensate for ambient temperature; however, the compensating bimetal is conventionally coupled directly with the valve member or valve stem thereby failing to solve the problemof gradual opening and closing of the valve.

Furthermore, the use of an ambient temperature compensating bimetal creates a problem in that heat from the motor bimetal adversely affects the ambient temperature compensating bimetal. This problem is remedied in some prior art heatmotor operators by attempting to overpower the heat leaking from the motor bimetal to the ambient temperature compensating bimetal with largetemperature differences. The result is that proper ambient temperature compensation is obtained only within limited ambient temperature ranges and limited energization and deenergization times; and, for longer energization and deenergization times, actuation and deactuating times of the heatmotor will vary greatly.

Another problem that exists with conventional heatmotor operators is that the heat obtained when the operating voltage is much greater than the nominal operating voltage causes gradual opening and closing and adversely affects operation in the same manner as high and low ambient temperature and long energization times. Similarly, the reduction in heat when the applied voltage is at a value much lower than the nominal operating voltage creates longer actuating and deactuating times than are desirable.

Accordingly, it can be seen that problems exist with respect to the utilization of heatmotor operators with gas valves, particularly in providing ability to operate safely and to close and remain closed under abnormal operating conditions. These problems are particularly acute in solid-state systems since less power is available for normal operation, yet the same range of abnormalities exists.

I SUMMARY OF THE INVENTION Accordingly it is an object of the present invention to construct a heatmotor operator that operates accurately under variable conditions such as appliedvoltage, energization time and ambient temperature. r

Another object of the present invention is to maintain snapacting operation of a heatmotor operator under adverse conditions. i l

The present invention has another object in that a snap-acting heatmotor operator requires less than full ambient temperature compensation by utilizing magnetic means to provide snap action.

A further object of'the present invention is to control the opening and closing of a valve with a lever which in turn is controlled by a bimetal assembly to thereby prevent tipping of the valve member and gradual opening'and closing of the valve. 5 p

Another object of the present invention is to control thermal conduction from a motor bimetal to a compensating bimetal in order to precondition a heatmotor operator for rapid deactuation even after long 'energization times.

A further object of the present invention is to construct a heatmotor operator that accurately operates with limited electrical power in order to permit its utilization with solid-state control circuitry. I

Heatmotor operators constructed in accordance with the present invention are advantageous over conventional heatmotor operators in. that snap action .is provided under adverse operating conditionssuch as long energization times, high and low ambient temperatures, and varying applied voltages. Actuating and deactuating times are maintained within predeter' mined limits regardless of adverse conditions since by utilizing a magnet for snap action complete ambient temperature compensation is not required therebypermitting bimetal deflection to be utilized for preconditioning.

The present invention is generally characterized in a heatmotor operator including first temperature responsive means connected with second temperature responsive means through insulating means, operating means including lever means connected with the second temperature responsive means, support means including pivot means connected with the lever means, and means for actuating the heatmotor operator.

Further objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in connection with the accompanying drawings. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top, plan-view of a first embodiment of a heatmotor operator in accordance with the present invention.

FIG. 2 is an elevational, sectional view with parts broken away of the embodiment of FIG. ltaken along lines 2-2.

FIGS. 3, 4, 5 and 6 are simplified, schematic representations of the embodiments of FIG. 1 during various stages of operation.

FIG. 7 is an elevational, sectional view with parts broken away of a second embodiment of a heatmotor operator in accordance with the present invention.

FIGS. 8, 9 and 10 are simplified, schematic representations of the embodiment of FIG. 7 during various stages of operation.

FIG. 11 is an elevational, sectional view with parts broken away of a third embodiment of a heatmotor operator in accordance with the present invention.

FIG. 12 is a broken top view of theembodiment of FIG. 11.

FIGS. 13, 14, 15 and 16 are simplified schematic representations of the embodiment of FIG. 1.1 during various stages of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of heatmotor operators according to the present invention are shown as used to control a valve; how ever, it is clear that the present invention is not limited to valve actuators and may be used with any apparatus requiring precise actuation, such as electrical switches.

The heatmotor operator of FIGS. 1 and 2 is set in a casing having upstanding sidewalls 12, end walls 14 and a bottom wall 16 which is broken away in FIG. 2. A manual valve-opening assembly extends through an opening in bottom wall 16 and includes a rod 18 and a spring 20 disposed in compression between wall 16 and a-ring 22 attached to rod 18 to bias the end of rod I8 away from wall 16. Left end wall 14 has an annular supporting step 24 for accommodating the end of the heatmotor operator, and a screw 26 is adapted to threadedly engage a threaded bore in step 24.

The heatmotor operator includes a bimetal assembly having a motor arm 28 and an ambient temperature compensating arm 30, each of which comprises a bimetallic strip, Motor arm 28 and compensating arm 30 are assembled so that their responses to temperature variations are opposite; that is, motor arm 28 deflects in a direction opposite to the deflection of compensating arm 30 when the heatmotor operator is energized. Motor arm 28 isoffset to form a flat end 32, which may be secured to step 24 of casing 10 either directly or through an insulator 34, and a planar center strip 36 of motor arm 28 is right angled to form a flange 38. A heating element 40 is wound around center strip 36 and is adapted to be connected to any conventional electrical source, such as 24 volt AC stepped down from 1 10 volt AC through a pair of terminals, now shown, positioned on casing 10. At the location where motor arm 28 is offset, the bimetallic strip is cut so that the center portion may be-moved away from the side portions of the strip to accommodate a pivot pin 42 which extends across the entire width of motor are 28., l

Compensating arm 30 has a flanged end 44, and at its other end compensating arm 30 is cut to permit the sides 46 to be bent down while a tongue 48 extends forward to engage a lever 50. An insulator 52 isdisposed between flange 38 of motor arm 28 and flange 44 of compensating arm 30 and may be attached thereto in any conventional manner such as by rivets.

Lever 50 has two ears 54 at one end thereof each of which has an aperture therein to accommodate pivot pin 42 which is flattened at either end to assure the secure mounting of lever '50. A window 56 is cut out of lever 50 directly above compensating arm 30 and insulator 52 so that heat from compensating arm 30 may escape whereas heat from motor arm 28 is reflected off a reflective surface 58 of lever 50. Lever 50 is cut or stamped immediately above tongue 48 of compensating arm 30 so that a right angled flange 60 extends down to connect with tongue 48 of compensating arm 30. Flange 60 has a slot 62 therein, and tongue 48 extends through slot 62 in order to connect the bimetal assembly to lever 50 at both pivot pin 42 and flange 62.

An annular permanent magnet 64 is firmly attached to lever 50 beyond flange 60 by a cylindrical sleeve 66 in which is mounted an operator 68 by use of an adhesive such as Glyptal. Operator 68 is adapted to coaxially abut a valve stem 70 which is biased, such as by a valve spring, now shown, towards operator 68. The remainder of the valve means associated with valve stem 70 is conventional and has not been shown except for a portion of a housing wall 72 which has an annular opening 74 therein to permit communication between operator 68 and valve stem 70.

Attached to housing wall 72 is an armature piece 76 having a primary armature 78 and a secondary armature 80. Primary armature 78 underlies the entire area of magnet 64 whereas secondary armature 80 overlies only part of the area of magnet 64. Armature piece 76 is generally U-shaped and lies on its side, and the right-hand portion that connects the primary and secondary armatures has a large slot 82 therein through which a narrowed offset end 84 of lever 50 extends so that end 84 may be under the control of rod I8 for manual opening of the valve. The slotted portion of armature piece 76 is shaped to provide ridges 86 and 88 to reduce magnetic coupling between primary armature 78 and secondary armature 80 and so that should the shoulders where lever 50 is narrowed abut the slotted portion they will only come in contact with the ridges to reduce friction and prevent sticking.

The operation of the embodiment of FIGS. 1 and 2 will be described in conjunction with FIGS. 3, 4, 5 and 6 which are simplified representations of the bimetal assembly and lever 50 of the heatmotor operator of FIGS. 1 and 2 in various stages of operation.

The heatmotor operator of FIGS. 1 and 2 is shown between the position it will assume in its energized and deenergized states to facilitate description thereof. That is, in the deenergized state magnet 64 will be nearly in contact with primary armature 78, and in the energized state magnet 64 will be nearly in contact with secondary armature 80. It is desirable to provide a gap of a few thousandths of an inch between magnet 64 and armatures 78 and in order to prevent magnetic sticking due to the extremely high rate of change of field intensity at magnetic contact between pieces. To this'end, it is noted that lever 50 acts as a spacer between magnet 64 and secondary armature 80. If the valve means is closed when the heatmotor operator is deenergized, valve stem 70 will be stopped on a valve seat and the abutting of operator 68 with valve stem 70 spaces magnet 64 from primary armature 78. Similarly, if the valve means is open when the heatmotor operator is deenergized, valve stem 70 will be stopped in an open position to permit spacing of magnet 64 from primary armature 78. The spacing between magnet64 and primary armature 78 may be adjusted by adjusting the position of operator 68 in magnet 64.

FIG. 3 represents the heatmotor operator in its deenergized state at normal ambient temperature, and it is noted that motor arm 28 and compensating arm 30 are substantially linear in the deenergized state to cause magnet 64 to abut primary armature 78 which in turn causes operator 68 to depress valve stem 70 against the force of the valve spring to either open or close the valve associated with valve stem 70depending upon the design thereof.

Assuming the valve to be closed when the heatmotor operator is in its deenergized state, if it is desired to open the valve electrical power is supplied to the leads of heating element 40 through terminals disposed on casing 10. The heat emitted from heating element 40 causes motor arm 28 to deflect upward, as shown in FIG. 4, and when the deflection force of motor arm 28 along with the force of the valve spring overcomes the magnetic attraction between magnet 64 and primary armature 78 the heatmotor operator will snap into its energized state wherein magnet 64 is in contact with secondary armature 80 thereby opening the valve.

The deflection of motor arm 28 is transmitted to magnet 64 through lever 50 to which magnet 64 is secured and which is connected with compensating arm 30 at slotted flange 60. Thus, it can be seen that it is the pivoting of lever 50 around pin 42 which actuates the valve and that valve operator 68 is always a constant distance from pin 42 to prevent cocking valve stem 70 in its bushing which could cause sticking. Since the magnetic force between magnet 64 and primary armature 78 is a function of the square of the distance therebetween, after contact is initially broken, the speed of movement of magnet 64 is increased and as magnet 64 approaches secondary armature 80 the magnetic attraction therebetween will further increase speed. Thus, it is seen that the transition between the deenergized state and the energized state of the heatmotor operator is accomplished with a snap action As shown in FIG. 4, compensating arm 30 does not immediately respond to the heat from heating element 40, and this is accomplished due to insulator 52 and window 56 which is disposed substantially directly above compensating arm 30. The lackof response of compensating atm 30 assists in the snap action of the heatmotor operator in that if compensating arm 30 were to respond to the heat immediately it would deflect downward and oppose the upward deflection of motor arm 28. The insulation and snap-acting effect is further enhanced by theaction of reflective surface 58 of lever 50 to concentrate the heat to the motorarm.

After heating element 40 has been energized for a period of time, the heat therefrom begins to affect compensating arm 30, as shown in FIG. 5; however, the. response of compensating arm 30 is not great enough to cause the heatmotor operator to changestates due to insulator 52 and the heat loss to casing through screw 26 and insulator34. The use of insulator 34 permits the heat loss to casing 10 to be controlled by varying the dimensions and material of the insulator. The

downward deflection of compensating arm 30 during the energized state of the heatmotor operator acts to precondition the bimetal assembly for quick transition to the unenergized state once the power supplied to heating 'element'40 is terminated.

When power to heating element 40 ceases, the heatmotor operator returns to its deenergized state, as shown in FIG. 6, due to the preconditioning action of compensating arm 30, the downward deflection of motor arm 28 with the termination of heat from heating element 40, and'the .magnetic attraction between primary armature 78 and magnet 64. The cooling of motor arm 28'is rapid due to the'thermal contact with casing 10 through screw 26 and insulator The transitionto the deenergized state is accomplished with snap action due to the magnetic interaction, and the heatmotor operator will return to the condition of FIG. 3 from the condition of FIG. 6 once sufficient time has elapsed to permitcooling of compensating arm 30.

If it is desired to manually open the valve, rod 18 may be permitted to be forced up by spring 20 to push offset end 84 of lever 50 up to engage the upper edge of slot 82 and thereby raise operator 68 to open the valve.

The use of the magnet 64 and the primary and secondary armatures permits the construction of a sturdy, accurate heatmotor operator as well as providing snap action. Ambient temperature compensation is provided byv the deflection in opposite directions of the motor bimetal 28 and compensating bimetal 30 in response to temperature, and one of the advantages of the heatmotor operator is that the bimetal assembly need not be fully'ambient temperature compensated due to the control of the operator by magnetic interaction. That is, high and low ambient temperature compensation is made much less critical by the magnetic characteristics of the heatmotor operator. I

The electrical power supplied to the leads of heating element 40 may be under the control of a mechanically acting electrical switch, such as a thermostat, in which case it is conventional to supply a voltage of 24 volts AC.

FIG. 7 is an elevational view-in section of a second embodiment of the present invention designed specifically for use with solid-state control circuitry. Parts utilized in the embodiment of FIG. 7 which are identical to parts utilized in the embodiment of FIG. 2 are given identical reference numerals, and similar parts are given reference numerals with IOO added. 1

The embodiment of FIG. 7 differs from the embodiment of FIG. 2 in that the bimetal assembly is constructed so that the motor arm is connected with lever 50 and thev compensating arm is secured to pin 42 and casing 10, and in describing the embodiment of FIG. 7, those identical parts described above with respect to embodiment of FIG. '2 will not be described again. The differences in the embodiments of FIGS. 2 and 7 are occasioned by the need for a heatmotor operator that can operate with limited electrical power supplied to the heating element in order to accommodate solid-state control circuitry, and by the desirability of longer turn on and turn off times.

The bimetal assembly of FIG. 7'comprises a bimetal motor arm 128 and a bimetal compensating am 130 which are connected together through insulator 52 that is disposed between a flange 138 of motor arm 128 and a flange 144 of compensat ing arm 130. Compensating arm 130 is offset at one end 101 so that it may be secured to casing 10 at step 24 by screw 26. While no insulator is shown disposed between offset end 101 of compensating arm I30 and step 24, it is apparent that should it be desired to reduce the heat transfer from compensating bimetal 130 to casing 10 an insulator may be utilized. At offset end 101, compensating bimetal 130 is cut so that the side portions may be depressed and the center portion raised to accommodate pivot pin 42 which'is inserted through the space therebetween.

Motor arm 128 is cut so that outer sides 103 may be bent down to permit a center extending tongue 105 to engage a slot 62 in lever 50. A heating element'l40 is wound around motor arm 128 and-covers as much of the motor arm as is possible in order to generate maximum heat with the limited power available from a solid-state control circuit. Heating element 140 is adapted to be connected to a pair of terminals on casing 10, which terminals may be connected to the solid-state control circuitry. a

The operation of the heatmotor operator embodiment of FIG. 7 will be explained in conjunction with FIGS. 8, 9, and 10 which are simplified representations of the bimetal assembly and lever 50 of the heatmotor operator of FIG. 7 in various stages of operation.

In the deenergized state at normal ambient temperature, the heatmotor operator is as shown in FIG. 8; that is, magnet 64 is in contact with primary armature'78 due to both the compensating arm 130 and the motor arm 128 being linear. When power is supplied from the solid-state control circuitry to heating element 140, the heat generate by heating element causes motor arm 128 to deflect upward,as shown in FIG. 9,

and this deflection acting on lever 50 along with the force' from a valve spring, now shown, associated with valve stem 70, causes magnet 64 to break contact with primary armature 78 and move toward secondary armature 80. Due to the fact that the magnetic attraction between magnet 64 and primary armature 78 decreases as the square of the distance therebetween snap action is provided in the transition of the heatmotor operator from the deenergized state to the'energized state. Furthermore, the snap action isenhanced by the attraction of magnet 64 to secondary'armature 80 which increases with the square of the distance therebetween as magnet 64 moves closer.

As can be seen from FIG. 9, compensating arm 130 has remained linear during the initial supply of power to the heatmotor operator. This is due to the insulation between motor arm 128 and compensating arm 130 provided by insulator 52 along with the connection of offset end 101 of compensating arm 130 with casing 10 whichprovides good thermal conductivity. However, as heat builds up at motor arm 128, compensating arm 130 does deflect, but only slightly due to the heat transfer to casing 10 and usual convection and radiation losses, as shown in FIG. 10.

Due to the speed at which solid-state components operate, the response of the heatmotor operator of FIG. 7 is not required to be as fast as the response of the heatmotor operator of FIGS. 1 and 2, and thus there is no need for a large deflection of compensating arm 130 to provide preconditioning when the heatmotor operator is in its energized state. Furthermore, the fact that motor arm 128 is not thermally connected with casing 10 does not adversely affect operation due to the permitted and desired slower operating speeds. The cooling of motor arm 128 is therefore slower than the cooling of motor arm 28 of FIG. 1 even though motor arm 128 is subjected to less heat than motor arm 28 of FIG. I.

When the power supplied to heating element 140 is. terminated, the cooling of motor arm 128 causes magnet 64 to break contact with secondary armature 80 and make contact. with primary armature 78 with snap action due to magnetic attraction. Compensating arm 130, due to its good thermal conductivity, cools as fast as motor arm 128, and thus the heatmotor operator reverts to the condition shown in FIG. 8 which. permits accurate operation of the heatmotor operator with short deenergized periods.

The magnetic interaction between magnet 64 and armature piece 76 permits the heatmotor operator of FIG. 7 to be snap acting under abnormal ambient temperature conditions without full bimetal ambient temperature compensation. Compensating arm 130 will not deflect sufficiently to adverse ly affect the accuracy of operation of the heatmotor operator during long energization times or when high voltages are supplied to heating element 140 due to the thermal connection with casing 10 at step 24 and convection and radiation losses.

A third embodiment of the present invention is shown in FIG. 11, which is an clevational view in section, and is designed specifically for use with solid-state control circuitry. Parts utilized in the embodiment of FIG. 11 which are identical to parts utilized in the embodiment of FIG. 2 are given identical reference numerals with 200 added.

The bimetal assembly of the heatmotor operator of FIG. 11 differs from the bimetal assembly of the heatmotor operator of FIG. 2 in order to provide accurate operation with the limited electrical power available from the solid-state circuitry and further to provide desired longer turn on and turn off times.

As shown in FIG. 11 the bimetal assembly has a V configuration with a bimetal motor arm 228 and a bimetal compensating arm 230 being joined through an insulator 252 at the apex of the V. Motor arm 228 is offset at one end 201 and has a narrowed portion 203 looped around a pivot pin 42. A free end 205 of motorarm 228 has a narrow tab 207 thereon which is inserted through a slot 209 in a wall of a cylindrical retainter element 240 is wound around a substantial portion of motor arm 228 and is adapted to be connected to a source of electrical power through the solid-state control circuitry.

Compensating arm 230 is cut at one end to permit sides 246 to bebent'down while a tongue 248 extends through a slot 62 in a flange 60 of a lever 250. The other end 215 of compensating arm 230 is secured to offset end 201 of motor arm 228 through insulator 252 by any conventional means such as rivets.

Pivot pin 42 is supported by a mounting bracket 217 that is secured to step 24 of casing 10 by a screw 26, as shown in FIG. I 12. Lever 250: is mounted on pivot pin 42 through a pair of I ears, as explained with respect to the heatmotor operator of FIGQZ and looped portion 203 of motor arm 228 is disposed around pivot pin 42 between the ears of lever 250. Arms 219 and 221 extend from mounting brackets 217 to keep the bimetal assembly centered. An insulator may be inserted between mounting bracket 217 and step 24 if it is desired to limit the thermal conductivity therebetween.

Lever 250 differs from lever 50 of the heatmotor operator of FIG. 2 in that no window is provided above compensating arm 230. Ambient temperature may be accurately sensed by compensating arm 230 through the open end of lever 250 adjacent mounting bracket 217 since motor arm 228 is not disposed between the open end of the lever and the compensating arm as in the embodiment of FIG. 2.

The operation of the heatmotor operator of FIG. 11 will be described in conjunction with FIGS. 13, 14, and 16 which are simplified representations of the bimetal assembly and lever during various stages of operation.

As explained with reference to the heatmotor operator of FIG. 2, magnet 64 is shown in a position between the positions assumed when the heatmotor operator is energized and deenergized. In FIG. 13 the heatmotor operator is shown in the deenergized state at normal ambient temperature and accordingly both motor arm 228 and compensating arm 230 are linear and magnet 64 is maintained in contact with primary armature 78.

FIGS. 14 and 15 show the heatmotor operator in the deenergized state under high and low ambient temperatures, respectively. The bimetal structures of motor arm 228 and compensating arm 230 are arranged such that the motor and compensating arms deflect in the same direction in response to temperature; however, lever 250 will not move in response to high or low ambient temperatures because the bowing or deflecting of the bimetal arms compensate for each other to maintain tongue 248 at the deenergized position. As shown in FIG. 14. an increase in ambient temperature causes motor arm 228 to bow upward since offset end 201 is stationary and tab 207 is movable only partially in and out of slot 209 and is not removable therefrom. The bowing of'motor arm 228 is aided by the rotation of looped portion 203 around pivot pin 42 and causes rotation of compensatingarm 230 where it is joined with motor arm 228; however. the downward deflection of compensating arm 230 in response to the increased ambient temperature prevents movement of lever 250 because tongue 248 is not moved. Similarly, the, downward bowing of motor arm 228 in response to decreased ambient temperature is compensated by the upward deflection of compensating arm 230 as shown in FIG. 15.

When the solid-state control circuitry is operated so as to supply electricity to heating element 240, the heatmotor operator will be placed in its energized state as shown in FIG. 16. The heatmotor operator is illustrated in FIG. 16 as operating under normal ambient temperature; however, operation under high and low ambient temperature will be similar due to the compensation described above with the aid of FIGS. 14 and 15. The heat from heating element 240 causesmotor arm 228 to bow upward; however, since this heat is not sensed by compensating arm 230, the rotation caused by the bowing of motor arm 228 causes compensating arm 230to apply an upward force to lever 250 which force combined with the force from a valve spring, now shown, associated with valve stem 70 causes magnet 64 to break from primary armature 78and move toward secondary armature 80. Since the magnetic attraction between primary armature 78 and magnet 64 decreases as the square of the distance therebetween, snap action is provided in the transition of the heatmotor operator from the deenergized state to the energized state. Furthermore, the snap action is enhanced by the attraction. of magnet 64 to secondary armature 80 which increases inversely with the square of the distance therebetween as magnet 64 moves closer.

Due to insulator 252 and normal convection and radiation losses, compensating arm'230 deflects only slightly when the heatmotor operator has been energized for prolonged periods. This is desirable since no preconditioning of the heatmotor operator, as shown in FIG. 5 with respect to the embodiment of FIG. 2, is required due to the speed of operation of the solid-state control circuitry.

When the supply of electricity to heating element 240 is terminated, motor arm 228 cools and straightens which rotates compensating arm 230 so as .to force lever 250 and magnet 64 away from secondary armature 80 and places the heatmotor operator in its deenergized state. The cooling of motor arm' 228 is not as fast as the cooling of motor arm 28 in the heatmotor operator of FIG. 2 since motor arm 228 is not directly thermally connected with casing 10; however, as previously mentioned, turn off times are'desirably longer with solid-state control circuitry. If faster turn off times are desired, retainer I 211 maybe integrally constructed with casing 10 or thermally connected therewith.

The slight deflection of compensating arm 230, as shown in phantom in FIG. 16, due primarily to radiated heat from heating element 240, provides sufficient preconditioning of the heatmotor operator, and compensating arm 230 does not deflect to a great extent during long energization times. The heatmotor is now in the deenergized state as shown in FIG. 13 and is in condition for recycling.

Pivot pin 42 independently supports the bimetal assembly, as well as lever 250; and, accordingly, the V configuration assembly of motor arm 228 and compensating arm 230 is free to pivot about pin 42 to permit extremely accurate and sensitive operation in response to temperature. Furthermore, the V configuration permits motor bimetal 228 to have increased length to permit greater work per degree of temperature change and, accordingly, per watt of electrical power.

As previously mentioned with respect to the embodiments of FIGS. 2 and 7, the magnetic interaction between magnet 64 and armature piece 76 permits the heatmotor operator to be snap acting during abnormal ambient temperature conditions without full bimetal ambient temperature compensation. The deflection of the compensating arm is' maintained at a minimum during long energization times and when high voltages are applied to heating element 240.

Inasmuch as the present invention is subject to many modifications. variations and changes in detail. it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

l. A heatmotor operator for controlling a casing comprising:

a bimetal assembly including first bimetal means and second bimetal means;

insulating means connecting said first bimetal means with said second bimetal means;

means for mounting said first bimetal means on the casing;

operating means including lever means having a first pora valve disposed in tion and a second portion. said first portion being connected with said second bimetal means; pivot means connected with said second portion of said lever means for pivotally supporting said lever means; said operating means including armature means. magnet means attached to said lever means, and a valve operator attached to said lever means and adapted to engage a control member of the valve; and

actuating means connected with said bimetal assembly and adapted to be connected to a source of electricity whereby said heatmotor operator is actuated to control the valve with snap action when electricity is supplied to said actuating means. v

2. The invention as recited in claim 1 wherein said armature means includes a primary armature and a secondary armature to provide snap action upon actuation andjdeactuation of said heatmotor operator.

3. The invention as recited in claim 2 wherein said actuating means includes a heating element disposed on said first bimetal means; said first bimetal means is arranged to deflect in a first direction in response to heat; and said second bimetal means is arranged to deflect in a second direction opposite to said first direction in response to heat whereby said second bimetal means acts to provide ambient temperature compensation for said bimetal assembly and to precondition said bimetal assembly for deactuation of said heatmotor operator.

4. The invention as recited in claim 3 wherein said lever means includes a reflective surface disposed above said first bimetal means and a window disposed above said second bimetal means whereby heat is concentrated at said first bimetal means and heat is dissipated from said second bimetal means through said window.

5. The invention as recited in claim 4 wherein said means for mounting said first bimetal means includes a screw to provide good heat transfer from said first bimetal means to the valve casing and an insulator disposed between said first bimetal means and the valve casing to limit heat transfer between said first bimetal means and the valve casing.

6. The invention as recited in claim 2 wherein said actuating means includes a heating element disposed on said second bimetal means; said second bimetal means is arranged to deflect in a .first direction in response to heat; and said first bimetal means is arranged to deflect in a second direction opposite to said first direction in response to heat whereby said first bimetal means acts to provide ambient temperature compensation for said bimetal assembly.

7. The invention as recited in claim 6 wherein said means for mounting said first bimetal means includes a screw to provide good heat transfer from said first bimetal means to the valve casing whereby said first bimetal means is capable of rapid cooling. 1

8. The invention as recited in claim 1 wherein said first bimetal means has a first end and a second end. second bimetal means has a first end and a second end. said insulating means is disposed between said first end of said first bimetal means and said first end of said second bimetal means, said mounting means for said first bimetal means includes a bracket supporting said pivot means and a retainer having a slot therein, said first end of said first bimetal is rotatably connected with said pivot means, said second end of said first bimetal means is inserted in said retainer slot. and said first portion of said lever means is connected with said second end perature compensated by the deflection of said second bimetal means.

10. The invention as recited in claim 9 wherein said actuating means includes a heating element disposed on said first bimetal means whereby bowing of said first bimetal means in response to the supply of electricity to said heating element causes said second bimetal means to move said lever means. 

1. A heatmotor operator for controlling a valve disposed in a casing comprising: a bimetal assembly including first bimetal means and second bimetal means; insulating means connecting said first bimetal means with said second bimetal means; means for mounting said first bimetal means on the casing; operating means including lever means having a first portion and a second portion, said first portion being connected with said second bimetal means; pivot means connected with said second portion of said lever means for pivotally supporting said lever means; said operating means including armature means, magnet means attached to said lever means, and a valve operator attached to said lever means and adapted to engage a control member of the valve; and actuating means connected with said bimetal assembly and adapted to be connected to a source of electricity whereby said heatmotor operator is actuated to control the valve with snap action when electricity is supplied to said actuating means.
 2. The invention as recited in claim 1 wherein said armature means includes a primary armature and a secondary armature to provide snap action upon actuation and deactuation of said heatmotor operator.
 3. The invention as recited in claim 2 wherein said actuating means includes a heating element disposed on said first bimetal means; said first bimetal means is aRranged to deflect in a first direction in response to heat; and said second bimetal means is arranged to deflect in a second direction opposite to said first direction in response to heat whereby said second bimetal means acts to provide ambient temperature compensation for said bimetal assembly and to precondition said bimetal assembly for deactuation of said heatmotor operator.
 4. The invention as recited in claim 3 wherein said lever means includes a reflective surface disposed above said first bimetal means and a window disposed above said second bimetal means whereby heat is concentrated at said first bimetal means and heat is dissipated from said second bimetal means through said window.
 5. The invention as recited in claim 4 wherein said means for mounting said first bimetal means includes a screw to provide good heat transfer from said first bimetal means to the valve casing and an insulator disposed between said first bimetal means and the valve casing to limit heat transfer between said first bimetal means and the valve casing.
 6. The invention as recited in claim 2 wherein said actuating means includes a heating element disposed on said second bimetal means; said second bimetal means is arranged to deflect in a first direction in response to heat; and said first bimetal means is arranged to deflect in a second direction opposite to said first direction in response to heat whereby said first bimetal means acts to provide ambient temperature compensation for said bimetal assembly.
 7. The invention as recited in claim 6 wherein said means for mounting said first bimetal means includes a screw to provide good heat transfer from said first bimetal means to the valve casing whereby said first bimetal means is capable of rapid cooling.
 8. The invention as recited in claim 1 wherein said first bimetal means has a first end and a second end, said second bimetal means has a first end and a second end, said insulating means is disposed between said first end of said first bimetal means and said first end of said second bimetal means, said mounting means for said first bimetal means includes a bracket supporting said pivot means and a retainer having a slot therein, said first end of said first bimetal is rotatably connected with said pivot means, said second end of said first bimetal means is inserted in said retainer slot, and said first portion of said lever means is connected with said second end of said second bimetal means.
 9. The invention is recited in claim 8 wherein said first bimetal means is disposed to deflect in a first direction in response to heat, and said second bimetal means is disposed to deflect in said first direction in response to heat whereby said first bimetal means bows due to the connection of said first end of said first bimetal means with said pivot means and the insertion of said second end of said first bimetal in said retainer slot such that said bimetal assembly is ambient temperature compensated by the deflection of said second bimetal means.
 10. The invention as recited in claim 9 wherein said actuating means includes a heating element disposed on said first bimetal means whereby bowing of said first bimetal means in response to the supply of electricity to said heating element causes said second bimetal means to move said lever means. 